Multi-step deposition of ferroelectric dielectric material

Abstract

Multi-step deposition of lead-zirconium-titanate (PZT) ferroelectric material. An initial portion of the PZT material is deposited by metalorganic chemical vapor deposition (MOCVD) at a low deposition rate, for example at a temperature below about 640 deg C. from vaporized liquid precursors of lead, zirconium, and titanium, and a solvent at a collective flow rate below about 1.1 ml/min, in combination with an oxidizing gas. Following deposition of the PZT material at the low flow rate, the remainder of the PZT film is deposited at a high deposition rate, attained by changing one or more of precursor and solvent flow rate, oxygen concentration in the oxidizing gas, A/B ratio of the precursors, temperature, and the like.

What is claimed is: 
     
       1. A method of fabricating an integrated circuit including a ferroelectric capacitor, comprising the steps of:
 depositing a first conductive film near a semiconducting surface of a body; 
 then depositing ferroelectric material over the first conductive film by metalorganic chemical vapor deposition comprising the steps of:
 for a first time duration, introducing precursors of lead, zirconium, and titanium, and a solvent, at a first collective flow rate, and an oxidizing gas, into a chamber containing the body; and 
 then, for a second time duration, introducing into the chamber the precursors of lead, zirconium, and titanium, and a solvent, at a second collective flow rate greater than the first collective flow rate, and an oxidizing gas; 
 
 depositing a second conductive film overlying the ferroelectric material; and 
 removing portions of the first and second conductive films, and the ferroelectric material, at selected locations, to define the ferroelectric capacitor. 
 
     
     
       2. The method of  claim 1 , wherein the first collective flow rate is at or below about 1.1 ml/min. 
     
     
       3. The method of  claim 2 , wherein the second collective flow rate is above about 1.1 ml/min. 
     
     
       4. The method of  claim 3 , wherein the second collective flow rate is in a range from about 1.5 ml/min. to about 2.5 ml/min. 
     
     
       5. The method of  claim 1 , wherein the step of introducing precursors for the first time duration is at a first flow ratio of a lead precursor to the sum of a zirconium precursor and a titanium precursor;
 and wherein the step of introducing precursors for the second time duration is at a second flow ratio of the lead precursor to the sum of the zirconium and titanium precursors that is higher than the first flow ratio. 
 
     
     
       6. The method of  claim 1 , wherein the oxidizing gas introduced for the first time duration comprises oxygen at a first concentration;
 and wherein the oxidizing gas introduced for the first time duration comprises oxygen at a second concentration higher than the first concentration. 
 
     
     
       7. The method of  claim 1 , further comprising:
 prior to the step of introducing precursors for the first time duration, heating the chamber containing the body to a susceptor temperature below about 640 deg C. 
 
     
     
       8. The method of  claim 7 , further comprising:
 after the step of introducing precursors for the first time duration, increasing the temperature in the chamber to a susceptor temperature above 640 deg C. 
 
     
     
       9. A ferroelectric capacitor in an integrated circuit, formed by a process comprising the steps of:
 depositing a first conductive film near a semiconducting surface of a body; 
 then depositing a first partial layer of ferroelectric material over the first conductive film by metalorganic chemical vapor deposition comprising the step of:
 for a first time duration, introducing precursors of lead, zirconium, and titanium, and a solvent, into a chamber containing the body at a first collective flow rate; and 
 depositing a second partial layer of ferroelectric material over the first partial layer by metalorganic chemical vapor deposition comprising the step of:
 for a second time duration, introducing the precursors of lead, zirconium, and titanium, and a solvent, into the chamber at a second collective flow rate greater than the first collective flow rate; 
 
 depositing a second conductive film overlying the ferroelectric material; and 
 removing portions of the first and second conductive films, and the ferroelectric material, at selected locations, to define the ferroelectric capacitor. 
 
 
     
     
       10. The capacitor of  claim 9 , wherein the first collective flow rate is at or below about 1.1 ml/min. 
     
     
       11. The capacitor of  claim 10 , wherein the second collective flow rate is above about 1.1 ml/min. 
     
     
       12. The capacitor of  claim 11 , wherein the second collective flow rate is in a range from about 1.5 ml/min. to about 2.5 ml/min. 
     
     
       13. The capacitor of  claim 9 , wherein the step of depositing the first partial layer introduces precursors for the first time duration at a first flow ratio of a lead precursor to the sum of a zirconium precursor and a titanium precursor;
 and wherein the step of depositing the second partial layer introduces precursors for the second time duration at a second flow ratio of the lead precursor to the sum of the zirconium and titanium precursors that is higher than the first flow ratio. 
 
     
     
       14. The capacitor of  claim 9 , wherein the process further comprises:
 during the step of introducing precursors for the first time duration, introducing into the chamber an oxidizing gas comprising oxygen at a first concentration; and 
 during the step of introducing precursors for the second time duration, introducing into the chamber an oxidizing gas comprising oxygen at a second concentration higher than the first concentration. 
 
     
     
       15. The capacitor of  claim 9 , wherein the step of depositing the first partial layer further comprises:
 prior to introducing precursors for the first time duration, heating the chamber containing the body to a susceptor temperature below about 640 deg C. 
 
     
     
       16. The capacitor of  claim 15 , wherein the step of depositing the second partial layer further comprises:
 increasing the temperature in the chamber to a susceptor temperature above 640 deg C.